The present invention relates to a closing, connecting and/or locking safety device, the locking occurring up to a limited tightening torque, said device also preventing non-destructive forced opening.
In particular, the invention relates to a safety cap capable of resisting non manifest acts of vandalism, wherein opening by unauthorized persons is nearly impossible (“vandal-resistant”) and wherein the tightening torque may at the same time be prevented from exceeding a threshold value (limited torque) during closure. A suitable threshold value is established during the designing phase in order to achieve a good seal without damaging the cap gasket. There is a need for a cap of this kind to close oil and/or fuel tanks of outdoor-operating equipment, (for example on a building site, on premises unprotected from incursions by prowlers), for example earthmovers, road machines, agricultural equipment, and other such equipment.
However, the invention may also be applied in other fields. For example, the device according to the invention is ideally suited to the fixing of swimming pool cover edges, the unauthorized or accidental removal of which is thereby effectively prevented, with remarkable safety advantages. The present invention provides a valuable and practical solution for the closure of holes and openings, the connection of co-axial elements or parts, and the locking or fixing of any kind of structure in many other applications requiring both limited tightening torque and prevention of non-destructive forced opening.
Further, vandal-resistant caps for tanks, which achieve the object through a keylock, are well known. Since a torque limiting device is not provided in these known devices, the torque applied during manual tightening is extremely discretionary, which causes an evident risk of deformation of the gasket, resulting in possible leakage of the tank contents. Moreover, in other known caps, substantially comprising two component parts (threaded connection and bell-shaped cap), opening is performed by unscrewing the caps only using a suitable key. These caps, however, are not really safe from acts of vandalism because, by applying adequate pressure to the bell-shaped element gripped during such operation, it is equally possible to unscrew the cap, due to the friction between the contact surfaces of the two elements. Furthermore, when operation of the cap is performed with a plastic key, the key itself may easily break. In similar known devices problems of the same kind exist. Moreover, the key shape in known devices allows the insertion in the seat of the key of ordinary tools too, such as screwdrivers, so that opening may still occur without the proper key.